Hormones and control of gluconeogenesis

Two key enzymes in the pathway are regnlated by interconversion cycles they are the regnlatory enzyme PFK-2, and the glycolytic enzyme pyruvate kinase. There are two separate protein kinases that phosphorylate these enzymes and they both resnlt in activation of these enzymes. Dephosphorylation inactivates them. 

These two kinase enzymes are involved in regulation of gluconeogenesis by hormones. 

An increase in cyclic AMP concentration activates protein kinase-A. The latter phosphorylates the following enzymes, which leads to an increase in the rate of gluconeogenesis. 

The role of glucagon and insulin in the regulation of glu-coneogenesis, along with other factors, is to maintain the blood glucose concentration in starvation. This is discussed in Chapter 12. 

Adrenaline increases the rate of gluconeogenesis it binds to the a-receptor on the surface of the liver cell, which results in an increase in cytosolic concentration of Ca ions (Chapter 12). This increases the activity of the Ca -catmodulin-dependent protein kinase which phosphory-lates and causes similar changes in the activities of the enzymes PFK-2 and pyruvate kinase to those resulting from activation of cyclic-AMP-dependent protein kinase. Hence Ca ions increase the rate of gluconeogenesis. 

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